The term "step over in basketball is used whenever a player steps out of bounds, or when a player steps over another one. Stepping over the line is as direct as it sounds, is when a player has his foot over the line, stepping over it, and is therefore out of bounds. Players do not step over the line on purpose, it is a mistake that leads to a turnover.
A player stepping over another is considered by many to be a disrespectful move, however it is part of the basketball culture. A player stepping over another means that the player is going over an opponent who is on the ground to get to his position.
Players step over others when a play such as a crossover or a poster dunk, plays that may leave the defender on the ground. Following the play, stepping over is a way of player to assert his dominance over the opponent, as demonstrated in a previous play.
One of the most famous step overs in basketball history was done by Allen Iverson during the 2001 NBA finals, where Iverson's 76ers faced the Lakers. Iverson was tightly guarded by Tyronn Lue, but still managed to shake him off his stance and hit a difficult corner shot. Lue ended up falling on the ground right at Iverson's feet, who then stepped over him in what became one of his most known career moments.